In Deutch




How to use a coal furnace


One of the oldest and still most common kind of heating plant for the home is the coal furnace.

A good coal furnace fired with high-grade fuel will give very satisfactory service with minimum effort on the part of the owner.

When people complain about the work required to coax heat from their coal furnaces, the fault is generally with the fuel, the chimney, or the manner in which the furnace is operated.

Efficient operation of any coal-burning furnace is largely dependent upon the chimney.

Any leaks about the chimney will interfere with the draft and prevent the furnace from working properly.

The stove pipe from the furnace to the chimney should slant upward and be sealed tightly into both furnace and chimney.

There are many minor points connected with operating a coal furnace that should not be overlooked, especially if you are having difficulty in keeping the furnace operating properly.

First of all, put only coal on the fire, never rubbish of any sort. Ashes should not be used, as they sometimes are, to bank the fire for the night. Never poke a fire, as this will mix the hot coals with the ashes and form clinkers.

If the basement is tightly shut, air will not circulate properly, the draft will be feeble, and the fire will burn poorly. Check to see that all the furnace doors shut tightly and that there are no leaks around the check damper when it is closed.

Fuel for a coal furnace

There are three kinds of coal used in the home coal furnace, anthracite, coke, and bituminous. Anthracite is probably the most widely used. It is very hard, and because it is low in volatiles it burns without smoke. It does not tend to swell and cake together as do some other coals, and it ignites easily.

Coal for furnace

Coke is similar to anthracite in that it burns without smoke, and it can be fired in much the same manner.

Bituminous is a soft coal, high in volatiles, and produces more smoke and soot than anthracite or coke. It is used mostly for industrial work.

In the United States, coal is graded according to size by passing it through screens or sieves of different sized mesh to separate the pieces. Each size is known by a specific name.

For a coal furnace, the following table shows the diameter of the mesh through which the largest piece of a given size of coal will pass. Thus, egg size coal will pass through a mesh which is 3 7/16 inches in diameter but not through one which is 2 1/2 inches in diameter. Stove coal will pass through a 2 1/2 inch but not a 1 9/16 inch mesh, etc.

Anthracite for a coal furnace

Name of size Diameter of mesh (inch)
Buckwheat (1)
Buckwheat (2)
4 1/2
3 7/16
2 1/2
1 9/16
1 1/16


more than 4
1 1/2
3 /4

Sizes of anthracite

The first consideration in burning anthracite in a coal furnace is to get the proper size for the furnace. Anthracite is obtainable in several sizes, and each size is best suited for a particular firebox.

  • Egg size is intended for fire pots not less than 24 inches wide and at least 16 inches in depth.
  • Stove coal is suited for fire pots 16 inches wide and 12 inches deep. Most home furnaces are designed to burn stove coal.
  • Chestnut is made for kitchen stoves and hot water boilers, where the fire pot is 10 to 16 inches deep and approximately 20 inches in diameter, and for furnaces with this size firebox.
  • Pea coal is used for kitchen ranges and water heaters, and can be used in the furnace, provided there is an excellent natural draft and special care is taken, when shaking the grates, not to allow the hot coals to fall.

The very small sizes, No. 1 buck wheat and No. 2 buckwheat, are intended for use in heating equipment with mechanical stoking devices and forced-draft blowers.

What size to burn in a coal furnace

Coal, or any fuel for that matter, must have air if it is to burn. Large-sized coal, when put in the firebox, will not pack very close together, and there will be ample space between each piece of coal for the circulation of air. Air enters from the bottom of the fire and must work its way through the entire fire bed.

Small-sized coal, put into a fire pot, packs to-together so that only a small amount of air can penetrate. If only a little air circulates, the fire will burn poorly and go out. Small-sized coal can be used for kitchen ranges or hot water heaters because the fire bed is not very deep.

While each furnace is best suited for one size of coal, it is possible to use a smaller size. This is generally done for the purpose of economy, as the smaller anthracite coals are somewhat cheaper per ton than the larger sizes. Using smaller coal in a coal furnace is also a very good means of retarding the fire during warm weather.

Lastly, it is sometimes impossible to get the larger coal in a coal furnace, and then the small sizes must do. When burning chestnut and pea coal, a somewhat thinner bed is required. These small coals pack quite densely, and if you try to build up a full fire pot with them, the fire will not burn very well. Probably the best method of burning small coal is to mix it with the regular size.

This is done by putting on a layer of stove coal and then adding a layer of the smaller.

Start the fire with stove coal, and when this is burning well, add the first layer of small coal. In a furnace, the fire bed is many inches thick, and if small-sized coal is used exclusively, a blower should be provided to force the air up through the fire bed.



Heating a home



  • Boilers
  • Chimneys
  • Coal furnace
  • Condensation
  • Fireplaces
  • Fuel economy
  • Furnace damper
  • Heat loss
  • Home insulating
  • Hot water
  • Insulation
  • Oil burners
  • Maintenance
  • Radiators
  • Regulators
  • Steam heating
  • Thermostat
  • Warm air
  • Winterproofing
  • Wood burning
  • Home Construction